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        쥐 - 뇌의 히스타민 - N - 메칠전달효소의 정제와 일반 특성 연구

        최명언,임혜원 생화학분자생물학회 1993 BMB Reports Vol.22 No.4

        Histamine-N-Methyltransferase (HMT: E.C. 2.1.1.8) was purified by the methods of ammonium sulfate fractionation, DEAE-cellulose chromatography, hydroxylapatite chromatography, and gel filtration on Sephadex G-75. Overall purification was 280-fold with a recovery of 8%. The activity of HMT was determined by radioisotopic method with [^(14)CH₃]S-adenosylmethionine(SAM). The labelled SAM was prepared by rat liver SAM synthetase with [^(14)CH₃]-methionine. The specific activity of prepared HMT was 3.9 nmol/min/㎎ protein at pH 8.5. The K_m values of histamine and SAM were 12μM and 40μM, respectively. It was also examined the effects of some modification reagents on the enzyme activity. p-Chloromercuribenzoate and N-ethylmaleimide inhibited the enzyme activity, while iodoacetic acid, iodoacetamide and succinic anhydride activated the enzyme activity.

      • SCIESCOPUSKCI등재

        Enzymatic Preparation of radiolabelled S - Adenosyl -L- [methyl-14C] methionine

        최명언,박인원,임혜원 생화학분자생물학회 1995 BMB Reports Vol.24 No.5

        S-Adenosylmethionine (SAM) serves as the major methyl group donor in biological system. This study describes an upgrade method for radiolabelled biosynthesis of SAM by methionine adenosyltransferase (MAT) in the presence of ATP and L-[^(14)C-methyl]methionine. The MAT was partially purified from rat liver and reoptimized the assay condition. The final yield of biosynthesis was better than 90% with relatively high specific radioactivity.

      • SCIESCOPUSKCI등재

        Bacillus amyloliquefaciens α - amylase 의 구조적 안정성에 대한 분광학적 및 전기영동 연구

        최명언,서세원,김광희,오화섭 생화학분자생물학회 1994 BMB Reports Vol.24 No.2

        The nature of calcium ion binding to α-amylase from Bacillus amyloliquefaciens was examined to investigate its effect on the structural stability of the enzyme. Calcium ion provided an excellent protection against the destruction of the enzyme activity by heat, protease, and denaturing agents. The structural change of α-amylase upon binding of Ca^(2+) has been studied by circular dichroism, fluorescence, and UV difference absorption spectroscopy. Upon binding calcium ions, the content of α-helical structure of α-amylase increased significantly and the binding constant of calcium to α-amylase was found to be about 4.8 mM at pH 7.5. The fluorescence emission spectrum showed that the calcium-free enzyme had different λ_(max) from the native enzyme. The λ_(max) of the Ca^(2+)-free enzyme shifted to longer wavelength by 15 nm and the intensity at λ_(max) decreased compared to the native enzyme. Furthermore, the protective nature of calcium ion binding was examined by electrophoretic techniques. The fragmentation pattern of α-amylase following an irreversible thermoinactivation at 90℃ was analyzed by SDS-PAGE. The native and calcium-free enzymes showed a marked difference in the electrophoretic patterns. In the case of native enzyme, the aggregate of the main band (54.7 kD) appeared gradually as high-molecular mass traces on the top region of the gel. However, in the case of Ca^(2+)-free enzyme, the main band disappeared rapidly and new distinct bands of smaller molecular masses (40.2 kD, 22.0 kD, 13.1 kD) appeared. The digestion patterns of α-amylase by trypsin were also different between the native and Ca^(2+)-free enzyme. From these results it can be concluded that the binding of Cat' ion contributes markedly to the structural stability of α-amylase.

      • SCIESCOPUSKCI등재

        쥐 뇌의 용해단백질 황산기 전달효소의 식별과 부분특성 연구

        최명언,이지오 생화학분자생물학회 1993 BMB Reports Vol.17 No.3

        Protein sulfotransferase (S) in soluble fraction of rat bran were characterized using [^(35)S] phosphoadenosinephosphosulfate (PAPS) as sulfate donor. [^(35)S] PAPS, the universal sulfate donor, was prepared enzymatically in rat liver high speed supernatant with carrier free ^(35)S0₄ and ATP. The activity of soluble protein sulfotransferase was observed in assay system containing [^(35)S] PAPS, Tris-maleate buffer pH 6.7 and soluble proteins from rate brain. The sulfated proteins were separated by SDS-PAGE and acid treatment was performed on the gel to differentiate tyrosine sulfate from carbohydrate sulfate. Incorporation of sulfate into tyrosine residues of proteins of various molecular weights was observed. Particularly high molecular weight ($gt;200 kD) proteins were more intensively sulfated. Effects of incubation time, temperature, pH, amounts of proteins, PAPS concentration, various metal ions, and some polyamino acids on the activities of protein sulfotransferases were investigated. These general properties of the soluble sulfotransferase were mostly distinct from those of the microsome associated sulfotransferase.

      • SCIESCOPUSKCI등재

        쥐 뇌의 Peroxidase 활성도 : 세포내 및 뇌 부위별 분포 Subcellular and Regional Distributions

        최명언 생화학분자생물학회 1988 BMB Reports Vol.15 No.4

        The peroxidase activity of rat brain was determined by spectrophotometrically using o-dianisidine as substrate. Basic assay conditions were optimized in order to eliminate the pseudoperoxidase activity. The peroxidase activities were then examined in subcellular fractions as well as in six different regions of the brain. It was found that a major part of the activity was associated with particulated fractions. The specific activity of the microsomal enzyme was roughly twice as high as that of the mitochondrial. The regional distribution of the microsomal activity was quite variable. The highest activity was found in the medulla oblongata and lowest in the striatum. The possible role of the brain peroxidase was birefly assessed.

      • SCIESCOPUSKCI등재

        Microsomal Cholesterol Esterase of Rat Brain : An Integral Membrane Protein

        최명언 생화학분자생물학회 1987 BMB Reports Vol.14 No.2

        The biological function of reverse transcriptase in RNA tumor viruses is to catalyze synthesis of the DNA provirus, the copy of the viral RNA genome which is integrated into the host DNA. Recently, this enzyme has also been useful in genetic engineering, in which the enzyme is used for the synthesis of a certain valuable gene from the eukaryotic mRNA. Most purified reverse transcriptases from avian, rodent, feline, and simian RNA tumor viruses exhibit two enzyme activities: RNA-dependent DNA polymerase and RNase H. Two forms of reverse transcriptase have been purified from avian myeloblastosis virus and Rous sarcoma virus, and their structural relatedness between these two was observed by peptide mapping. In mammalian retroviruses, we observed so far only one species enzyme, which requires either Mn^(2+)or Mg^(2+) ion as a cation. The RNase H activity appears to be located on the separate location of the molecule and more stable. The results of radioimmunoassay showed that the reverse transcriptase contains two or three kinds of antigenic determinants.

      • SCIESCOPUSKCI등재

        벤질아민을 기질로 사용한 뇌 Monoamine Oxidase 의 기초 성질

        최명언,박희섭 생화학분자생물학회 1989 BMB Reports Vol.16 No.3

        Monoamine oxidase (MAO) of rat brain was assayed by spectrophotometric method using benzylamine as substrate. Basic assay condition was optimized and the specific activity of prepared mitochondrial fraction was 2 nmoles/㎎ protein/min. under the standared condition. In order to correlate the MAO activity with the physico-chemical state of mitochondria, the enzyme activity was assayed in the presence of various chemicals known to affect the metabolic state of mitochondria. Among the tested, the proton and Ca^(+2) ion exibited interesting results. When pH was altered from 7.2 to 9.0, the activity of the brain MAO increased more than twofold and the calculated Km value at the alkaline pH was about 5 times smaller than that of neutral pH. Thus the Vmax/Km profile indicates that the neutral molecule appears to be the active substrate. Ca^(+2) ion showed moderate activation of the brain MAO activity at pH 7.2×9.0 in Tris-HCl buffer. When the mitochondrial MAO was solubilized with Triton X-100, the Ca^(+2) ion effect disappeared.

      • SCIESCOPUSKCI등재

        쥐 뇌 Microsome 의 용해된 Cholesterol Ester Hydrolase 의 반응속도론적 경향

        최명언 생화학분자생물학회 1989 BMB Reports Vol.16 No.4

        Microsomal cholesterol ester hydrolase of rat brain has been solubilized with good yield and stability. The optimal solubilization was achieved by homogenization and high speed centrifugation of microsomes at 10 ㎎ dry weight/㎖ of Tris-HCl buffer, pH 7.6, containing 0. 75 % Triton X-100. The solubilized enzyme was more dependent on exogenous lipid for activity than the microsome-bound enzyme, but the optimal concentration of Triton X-100 was greatly reduced. Series of experiments, in with concentrations of Triton X-100, the substrate, and the solubilized enzyme were varied independently, suggested that the activation effect of the detergent depended more on the ratio of detergent to enzyme than on the ratio of detergent to substrate. The observed role of detergent is helpful to evaluate the kinetic behavior of the enzyme in the presence of detergent.

      • SCIESCOPUSKCI등재

        지질을 제거한 쥐 뇌의 Monoamine Oxidase 의 용해와 특성 연구

        최명언,정성권 생화학분자생물학회 1991 BMB Reports Vol.18 No.3

        In order to investigate the nature of lipid-protein interactions of monoamine oxidase (MAO) of rat brain, the membrane-bound MAO was solubilized with Triton X-100 after depletion of mitochondrial lipid by organic solvents. Extraction with chloroform and acetone removed 9696 of total lipid from mitochondria, while there was no apparent change in enzyme activity. Reactivation was performed by interacting the defined phospholipids with the solubilized MAO. The basic properties of the reactivated enzyme were compared with those of both membrane-bound and solubilized enzyme. It was found that phosphatidylcholine was the activator for the solubilized enzyme with 90% activation at the lipid to protein ratio of 6 to 1. When reactivated the stability of the enzyme improved greatly at 37� and the pH optimum of the solubilized enzyme shifted to that of the membrane-bound enzyme. While K_m value of 0.18 mM of the solubilized enzyme altered to 0.12 mM upon reactivation, the value of V_(max) remained unchanged. It seems that this system could provide a series of basic informations on the roles of phospholipids in rat brain MAO and the nature of the interactions between membrane-bound proteins and their environmental phospholipids.

      • SCIESCOPUSKCI등재

        쥐 뇌의 아릴설파타아제 A 의 Sepharose 4B에의 고정화

        최명언,정제훈 생화학분자생물학회 1992 BMB Reports Vol.20 No.4

        Rat brain arylsulfatase A monomer was immobilized to CNBr-activated Sepharose 4B. The coupling of the enzyme could be accomplished up to the degree of 99%. The general properties of the immobilized arylsulfatase A were compared with those of the soluble enzyme. The enzymatic activity of the enzyme was conserved well by immobilization and the catalytic properties of the immobilized enzyme were similar to the soluble one except the increased Km value and the improvement of stabilities toward heat and pH. Thus the covalent coupling of the enzyme to Sepharose 4B did not affect vitally the functional groups of the active site of the enzyme. The two-pH optima profile of the immobilized enzyme imply that the multiple pH optima of the arylsulfatase A could not be explained solely by the monomer-dimer association.

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